Çocuklara iyi geceler dedim.

Because çocuklara means to the children.

It breaks down like this:

• çocuk = child
• çocuklar = children
• çocuklara = to the children

The ending -a / -e is the dative case, which often corresponds to to in English.

So:

• Çocuklar iyi geceler dedim would be incorrect here.
• Çocuklara iyi geceler dedim correctly shows who you said it to.

It has three parts:

• çocuk = child
• -lar = plural ending, so children
• -a = dative ending, so to

So:

• çocuk + lar + a = çocuklara

The form is -lar rather than -ler because of vowel harmony: the last vowel in çocuk is u, which is a back vowel, so the plural becomes -lar.

Then the dative is -a rather than -e, again because of vowel harmony.

Dedim means I said.

It comes from the verb demek, which means to say.

In this sentence:

• de- = verb stem
• -di = past tense
• -m = I

So dedim = I said.

This verb is a little irregular, so you get dedim, not something like demdim.

Because Turkish usually includes the subject inside the verb ending.

In dedim, the -m already tells you the subject is I.

So Turkish often leaves out the pronoun when it is already clear.

Compare:

• dedim = I said
• dedin = you said
• dedi = he/she/it said
• dedik = we said

You could say Ben çocuklara iyi geceler dedim, but ben is not necessary unless you want emphasis.

Because iyi geceler is the normal fixed expression for good night in Turkish.

Even though geceler is plural literally, the whole phrase functions as one set expression.

So learners should treat it as a chunk:

• iyi geceler = good night

This is similar to how some expressions in languages do not translate word-for-word in a natural way.

It is the thing that was said.

The sentence is basically:

• to the children
  • good night
    • I said

So iyi geceler is the content of the speech.

With verbs like demek, Turkish often places the actual words spoken directly before the verb, without needing extra marking in simple sentences like this.

Because demek is very natural when reporting the exact words you said, especially short expressions like greetings.

So iyi geceler dedim is the most natural way to say I said good night.

Söylemek also means to say / to tell, but it is often used a bit differently. For example, it is common for conveying information, instructions, or statements.

So:

• Çocuklara iyi geceler dedim = very natural
• Çocuklara iyi geceler söyledim = possible in some contexts, but less natural for this simple greeting

For a learner, the safest choice here is demek.

Because diye is often optional when reporting short direct speech, especially common expressions.

You can say:

• Çocuklara iyi geceler dedim.

And that is completely natural.

In other contexts, diye can help mark the quoted content more explicitly, but it is not required here.

The sentence uses a very normal Turkish word order:

• Çocuklara = to the children
• iyi geceler = good night
• dedim = I said

Turkish often puts the verb at the end, so dedim comes last.

The rest of the sentence can sometimes move around for emphasis, but this version is very natural and neutral.

Not naturally in English.

Even though geceler is plural in form, the Turkish expression iyi geceler simply means good night as a fixed phrase.

So the natural translation is:

• I said good night to the children.

Not:

• I said good nights to the children.

A simple approximate pronunciation is:

cho-jook-lah-rah ee-yee ge-je-ler deh-deem

A few helpful notes:

• ç sounds like ch in chair
• c sounds like j in jam
• ı is a vowel that does not exist in English; it is a dull, central vowel
• i is like ee
• d in dedim is a normal d

So:

• Çocuklara ≈ cho-jook-lah-rah
• iyi geceler ≈ ee-yee ge-je-ler
• dedim ≈ deh-deem

In normal usage, that is the clear meaning.

Because:

• çocuklara marks the recipient
• iyi geceler is a fixed nighttime farewell
• dedim means I said

So the sentence naturally means that you addressed the children and said good night to them.